1. Field of the Invention
This invention is concerned with the breaking or resolution of oil-in-water (O/W) bituminous emulsions by treatment with water soluble mixed ethylene oxide/propylene oxide polyols of relatively high molecular weight containing ethylene oxide and propylene oxide.
2. Description of the Prior Art
A great volume of hydrocarbons exist in known deposits of tar sands. These deposits occur at various places, the Athabasca tar sands in Canada being an example. The petroleum in a tar sand deposit is an asphaltic bitumen of a highly viscous nature ranging from a liquid to a semi solid. These bitumeninous hydrocarbons are usually characterized by being very viscous or even non flowable under reservoir conditions by the application of driving fluid pressure.
Where surface mining is not feasible, the bitumen must be recovered by rendering the tar material mobile in situ and producing it through a well penetrating the tar sand deposit. These in situ methods of recovery include thermal, both steam and in situ combustion and solvent techniques. Where steam or hot water methods are used, a problem results which aggravates the recovery of the bitumen. The difficulty encountered are emulsions produced by the in situ operations. These emulsions are highly stable O/W emulsions which are made even more stable by the usual presence of clays. Most liquid petroleum emulsions are water-in-oil (W/O) types. These normal W/O emulsions are broken by methods known in the art. However, the bitumen emulsions which are O/W types present a much different problem, and the same demulsifiers used in W/O emulsions will not resolve the O/W bitumen emulsions. The uniqueness of these O/W bitumen emulsions is described in prior art reference A: C. W. W. Gewers, J. Canad. Petrol. Tech., 7(2), 85-90 (1968). There is much prior art concerning the resolution of normal W/O emulsions. Some of the art even mistakenly equates bitumen O/W emulsions with these W/O emulsions. The following is a list of several additional art references.
B. N. Schonfeldt, Surface Active Ethylene Oxide Adducts, Pergamon Press, New York, 1969, Section 4.11.2, pp 577-582 describes the types of chemical demulsifiers used to treat standard crude oil emulsions of the W/O type. Included are the Pluronic surfactants having 20-30 wt. % ethylene oxide in the structure.
C. In U.S. Pat. No. 4,139,451, tar-water from a coking operation is demulsified with ##STR1## where m=2 or 3, n=12.
D. Chem. Abstr. 90 206927z discloses the use of ##STR2## where n=2.9 or 3.1 in H.sub.2 O to extract bitumen from Athabasca tar sands in the presence of kerosine, presumedly active because of its ability to stabilize the W/O emulsions formed.
E. Several Esso Patents by Canevari, et. al. (U.S. Pat. No. 3,296,117; 3,331,765; 3,893,907) disclose mechanical demulsification processes for tar sand emulsions involving mixtures of one or more of the following demulsifiers: acid esters of ethoxylated alkylphenol-formaldehyde condensates; amine alkoxylates from 40:60 to 60:40 mixtures of ethylene oxide and propylene oxide, and Pluronic type surfactants. In U.S. Pat. No. 3,893,907 the structure of applicable Pluronics is given. According to the structure given, molecular weight may vary from 1,000 to over 16,000 but ethylene oxide content (by weight) is impossible to gauge due to an apparent error in the chemical structure as given. No examples of the use of Pluronics could be found in any of these patents.
F. J. A. Richard (Esso), U.S. Pat. No. 3,330,757 is as E above, but surfactants (which may be sorbitan type, standard nonionics, or Pluronics) are recommended to be in the HLB range of 10-18.
G. Texaco Canada was granted a recent patent U.S. Pat. No. 4,058,453 for breaking tar sand emulsions using high molecular weight poly(ethylene oxides) of greater than or equal to 100,000 molecular weight with optional addition of an alkaline earth metal halide.
H. U.S. Pat. No. 3,553,100 (Shell Oil) discloses a method for breaking tar sand emulsions utilizing a chemical demulsifier "in which ethylene oxide groups, acyl radicals and from about 10 to 22 carbon atoms are contained in each of the molecules of a surfactant that exhibits a significant amount of solubility in both oil and brine." The surfactant is presumedly of the type ##STR3##
I. U.S. Pat. No. 3,334,038 (Petrolite) discloses an electrical-chemical process for breaking tar sand emulsions utilizing a chemical demulsifier, a polyester of a polyalkyleneether glycol and a polycarboxylic acid.
Related application, Ser. No. 152,452 filed of even date contains experimental evaluation of some of the prior art demulsifiers described above. That information is incorporated herein by reference.
It is an object of the present invention to provide a method whereby O/W bitumen emulsions may be broken by treatment with a class of mixed ethylene oxide/propylene oxide polyols which would not be useful in the breaking of normal W/O emulsions.